Demi Moore has gone to rehab because she is “emotionally and physically exhausted” over her painful split with Ashton Kutcher, who is “acting like a teenage boy,” say friends.

One tells us that Ashton continues to flirt with women while still calling Demi “when he is at a low moment.”

Ashton was partying with Brazilian supermodels at Sao Paulo fashion week while painfully thin Demi collapsed at her home Monday night. After being rushed to the hospital, she checked into a treatment facility Tuesday, where she was visited by her daughter Rumer Willis.

A source said, “Ashton has been very sloppy about his private life. He goes between doing ridiculous things and then making overtures to Demi. She took her marriage very seriously, she gave it 100 percent, and his behavior is confusing to her.

“Demi was talking to Kobe Bryant at a CAA Golden Globes party, and Ashton came over and made a scene. He made jealous comments to Kobe, then Ashton went to the bar and was openly flirting with other women.” Following their split, Ashton spent the holidays in Italy with screenwriter Lorene Scafaria.

The source continued, “Demi put up with a lot from Ashton — and despite the rumors, she always gave him the benefit of the doubt. But as soon as he admitted it, she asked him to leave. She helped him build his career, and as soon as he got his own success he became very full of himself. He was pushing and pulling at her for months before they split.

“Now he’s carrying on like a teenager, goes around with other women, and then, when he’s feeling scared and lonely, he reaches out to Demi. It’s really taking its toll on her. Demi is exhausted and humiliated. She needs some time to take care of herself and regroup.”

Demi’s rep declined to comment beyond her earlier statement, “Demi has chosen to seek professional assistance to treat her exhaustion and improve her overall health.”